What is a hecatomb?
In ancient Greece, a hecatomb (“ἑκατόμβη” / “hekatómbē”) was a sacrifice of 100 cattle (“Hekaton” = one hundred, “bous” = bull) to the Greek gods. During special religious ceremonies, hecatombs were offered to Greek gods Hera, Athena, and Apollo. At the end of the Olympic Games, a hecatomb was also offered to Zeus at Olympia. But in practice, the “100 cattle” requirement was not applied strictly.
The number was often relaxed: even as few as 12 animals could make up a hecatomb.
The type of animals used was not strictly observed. Although the sacrifice of cattle was specified in the early religious ceremonies of both Greeks and Romans; later "hecatomb" came to describe a large number of any kind of animals devoted for sacrifice.
Later the term became purely figurative. "Hecatomb" is used to describe the sacrifice or destruction by fire, tempest, disease or the sword of any large number of persons or animals; and also of the wholesale destruction of inanimate objects. It has even been applied to the destruction of mental and moral attributes.